X-ray fluorescence analysis is a well known and frequently used technique to rapidly analyze specimens for both the existence of certain elements and their relative magnitudes in sample compositions. In general, the specimen is illuminated by a source of X-rays, causing secondary X-ray emissions from the specimen which have distinct and measurable wavelength signatures attributable to the elements present. A dispersion crystal is then used to separate the secondary emission energy magnitudes at various wavelengths by transformation into energy magnitudes at distinct and separate angles; see FIG. 1. An X-ray counter/recorder is swept over the arc to obtain a signature for determination of the elements present and their relative magnitudes. For more details the reader is referred to the book X-RAY SPECTROCHEMICAL ANALYSIS by L. S. Birks, first published in 1959 by Interscience Publishers, Incorporated.
To best utilize such complex and expensive equipment in the repetitious analysis of numerous but similar test specimens, it is necessary to have a specimen holder and preparation apparatus which is fairly inexpensive, yet, can insure test results that are accurate and reproducible. Recognition of the deficiencies in available hardware is foremost in the development of the apparatus disclosed herein. It was the awareness that the control of surface flatness and specimen volume in a shallow sample holder are related to the accuracy and repeatability of X-ray fluorescence analyses, that precipitated the evolution of the disclosed apparatus.
General specimen holders are commercially available, e.g., the SPEX LIQUID SAMPLE CELL, General Electric Company part number A7011BE or Spex Industries part number 3515. The use of these types of holders was satisfactory in the past, but with refinements in test equipment and procedures to improve measurement accuracy such holders alone are inadequate to control specimen surface and volume parameters. In view of these deficiencies, many users of X-ray fluorescence equipment are attempting to develop specimen holders which are compatible with contemporary sampling rates and equipment accuracies.
An effective sample holder must include a mating apparatus which appropriately prepares the specimen face for X-ray analysis. This requires a device which will take a filled specimen holder having a sheet of plastic film draped over the sample face, squeeze out any trapped air bubbles, accurately level the exposed specimen face, stretch the film taut over the specimen, and allow the installation of a film holding ring while confining the specimen.